(a) Technical Field of the Invention
The present invention relates to a novel design of an ink cartridge structure, and in particular to an ink cartridge structure that comprises a resilient device for cushioning impact and thus protecting the ink cartridge from being damaged or incurring ink discontinuity, wherein the resilient device in arranged at an end of the ink cartridge and an upper end of the ink cartridge forms an internal thread to engage a threaded section formed on a connection bar for adjustability of the biasing force induced by the resilient device and thereby adjusting the force that the resilient device applies to the ink cartridge and wherein a vent hole is provided in the coupling between the resilient device and the ink cartridge so that when the resilient device is compressed, air is pumped into the ink cartridge through the vent hole to keep the ink contained in ink cartridge being driven toward a writing tip of the ink cartridge and discontinuity of ink supply is obviated.
(b) Description of the Prior Art
A conventional pen comprises a barrel in which an ink cartridge is received and fixed in position by threading engagement. Such a structure suffers easy damage to the writing tip or ball point of the ink cartridge due to the fact that no cushioning is provided to absorb impact energy that is applied to the writing tip or ball point when the writing tip is hit by for example an external force or falling onto the ground. When the ball point is damaged, the ball cannot roll smoothly and discharge of ink through the ball is interrupted. The worst case is that the pen is totally broken and cannot be used for writing. A solution to such a problem is a pen including a resiliently supported ink cartridge or ink tube as shown in FIG. 1 of the attached drawings, wherein a pen is composed of a hollow barrel 1 having an upper end forming a recess 11, an ink cartridge or ink tube 10 having an upper end forming a projection 101, and a spring 12. The spring 12 has an end received and retained in the recess 11 of the upper end of the barrel 1 and an opposite end supported on the projection 101 of the upper end of the ink cartridge 10 so that the ink cartridge 10 is subjected to the spring force of the spring 12 to resiliently extend and retract, whereby when the ink cartridge is subjected to an external impact, the spring 12 effects cushioning against the impact force by allowing the ink cartridge 10 to retract back into the barrel 1. Thereafter, when the impact is removed, the spring force of the spring 12 drives the ink cartridge outward for writing. In this way, the ink cartridge can be protected from damage caused by external impact. However, such a spring-cushioning ink cartridge has the following disadvantages:
(1) The assembly of the barrel 1 and the ink cartridge 10, as well s the spring 12, requires first fitting parts into the barrel 1 and then closing the barrel 1 by threading operation. This is certainly very troublesome.
(2) With the ink contained in the ink cartridge 10 fully consumed, the whole pen has to be disposed of and a new pen has to be purchased, because due to the assembly, there is no substitute ink cartridge 10 that is available individually. This makes the pen an uneconomic device.
(3) The lines drawn with the conventional ink cartridge is of a fixed width and the line may get easily broken when the force applied to the pen in the writing process is too light. Other disadvantage is also known for discontinuous line that a pen that has been stowed in an up-side-down manner for a substantial period of time may draw.
Thus, it is desired to provide an ink cartridge for pens to overcome the above drawbacks.